cliftyhanger
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| posted on 8/9/11 at 08:09 AM |
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Brake proportioning valve
Putting together (very slowly) my spitfire.
Long story short, it is using 245 capri vented discs and cortina sized calipers (actually GT6 ones, same pad as cortina and others) at the front, and
MGF rear discs/calipers which are about the same diameter.
I suspect I will have too much braking at the rear, so what can I use?? There are all sorts available, mondeo, mini as well as the adjustable ones.
Hoping to be nice and cheap, the mondeo etc ones seem to be a tenner new on the bay.
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MkIndy7
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| posted on 8/9/11 at 08:17 AM |
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No idea but hadn't you best be setting off soon?, Ferry to catch n'all 
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MikeCapon
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| posted on 8/9/11 at 08:43 AM |
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It's more expensive but you need to look for an adjustable valve. If you simply choose a fixed valve from another car your chances of it being
right, in terms of balance are very small. And then once fitted you're stuck.
An adjustable valve will enable you to choose your front/rear balance so your brakes work as they should.
This might seem a bit obvious but fitting one from a Mondeo is hardly likely to work. These are your brakes you're talking about after all.
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cliftyhanger
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| posted on 8/9/11 at 09:46 AM |
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quote:
Originally posted by MkIndy7
No idea but hadn't you best be setting off soon?, Ferry to catch n'all
Should have been ready by last easter. And booked into a trackday middle of November. Still a bare chassis, need to assmble the CV jointed shafts so
it can get on some wheels. Then the fun begins....
And the 10CR, bit soft I reckon. Especially as they now get 3 nights sleep
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cliftyhanger
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| posted on 8/9/11 at 09:49 AM |
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Oh, as for the valve.....
Some have done the mod and reckon OK without. However, is there a figure of what % the rear brakes should be? I suspect it varies car to car. However,
my thinking was that if another car ran similar sized brakes, then the valve would be a good match. And I really do not want the rears locking up
first.
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sheepish0001
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| posted on 8/9/11 at 09:54 AM |
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I used one like this on my Mini when I removed the compensator, lets you make it work nice for MOT and then i used to tweak it to nearly 50/50 so i
locked up front only a tiny bit before the backs
http://www.ecrater.co.uk/p/7182470/hot-rod-universal-chrome-adjustable
 
Brake Valve
Sheep
[Edited on 8/9/11 by sheepish0001]
[Edited on 8/9/11 by sheepish0001]
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Greenie
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| posted on 8/9/11 at 11:55 AM |
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Has anyone got a diagram of how this fit into the system?
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MikeCapon
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| posted on 8/9/11 at 12:06 PM |
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quote:
Originally posted by Greenie
Has anyone got a diagram of how this fit into the system?
These valves fit into the rear brake line. There are only two holes generally marked 'in' and 'out'. You don't really
need a diagram do you?
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sheepish0001
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| posted on 8/9/11 at 12:12 PM |
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quick sketch in paint hope it helps, im sure if i could fit one any one can 
 
Diag
Hope it helps
Shaun
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MikeRJ
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| posted on 8/9/11 at 12:32 PM |
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quote:
Originally posted by sheepish0001
I used one like this on my Mini when I removed the compensator, lets you make it work nice for MOT and then i used to tweak it to nearly 50/50 so i
locked up front only a tiny bit before the backs
On a mini that is a recipe for swapping ends in the blink of an eye if you hit a slippery patch of road whilst braking.
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hobbsy
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| posted on 8/9/11 at 01:31 PM |
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quote:
Originally posted by sheepish0001
I used one like this on my Mini when I removed the compensator, lets you make it work nice for MOT and then i used to tweak it to nearly 50/50 so i
locked up front only a tiny bit before the backs
http://www.ecrater.co.uk/p/7182470/hot-rod-universal-chrome-adjustable
Brake Valve
Sheep
[Edited on 8/9/11 by sheepish0001]
[Edited on 8/9/11 by sheepish0001]
I use one of these on my single master cylinder Fury (after fitting Wilwoods on the front) and once set up (by ragging it up and down the road and
stamping on the brakes) it works fine. Dual master cylinders would be better but at the moment not worth the cost / hassle.
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mad-butcher
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| posted on 8/9/11 at 01:42 PM |
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one point to remember using that type is that on some of them the threads are imperial not metric. not a problem really
tony
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cliftyhanger
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| posted on 8/9/11 at 03:44 PM |
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quote:
Originally posted by mad-butcher
one point to remember using that type is that on some of them the threads are imperial not metric. not a problem really
tony [/quote
I consider that an advantage 
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britishtrident
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| posted on 8/9/11 at 06:04 PM |
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quote:
Originally posted by MikeRJ
quote:
Originally posted by sheepish0001
I used one like this on my Mini when I removed the compensator, lets you make it work nice for MOT and then i used to tweak it to nearly 50/50 so i
locked up front only a tiny bit before the backs
On a mini that is a recipe for swapping ends in the blink of an eye if you hit a slippery patch of road whilst braking.
100% right on that MikeRJ on BL Minis you want sweet FA braking from the rear brakes if you value your life.
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mistergrumpy
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| posted on 8/9/11 at 06:28 PM |
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Another thing to note is that some of the cheaper ones ain't worth the money. I still have one amongst the pile of dust and crap in the garage
that was useless. It had a rubber washer on the screw plunger that when it was screwed down, turned inside out and just plugged the whole thing up.
Utter crap. Get a decent brand.
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britishtrident
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| posted on 8/9/11 at 06:44 PM |
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A complex subject with lot of factors involved.
Years ago people used to modify Lockheed pressure limiting valves from the 1960s-early 1970sMK1 & MK2 BL Mini with single circuit brakes. The
problem was the internal spring was soft with a high pre-load so the adjustment that was available was very limited unless the internal spring was
changed for a slightly shorter and higher rate spring.
Later load sensing valves such those used on some French and Itallian cars were modified --- I can't remember who was on the forum
discovered a Fiat Uno/Ritmo/Strada/Lada Riva valve was both very cheap could be very easily modified to an adjustable valve by simply adding an
external bracket with an adjuster bolt acting on the piston. Remember the adjuster will have to be rendered fixed for IVA.
A Mondeo or Fiesta or Corsa in line valve is a good simple solution for IVA purposes but it won't be fine tuned for maximum retardation.
Other common modern car with a brake proportioning valve in the rear circuit are the Rover 25 and 45 without ABS but this a dual circuit type with
two inlets and two outlets
What you could fit a Mondeo valve for IVA then fit and setup a Fiat/Lada valve afterwards.
Now a couple of caveats ---- most importantly setting up the brake bias requires care, be very cautious when road testing brake bias, always start
with excess front bias then gradually increase the rearward pressure setting. Always test at low speed first on a good dry clean road surface. When
you think you have found the perfect setting turn the bias back towards the front a little.
Second caveats is about some of the commercially available adjustable bias valves are not suited to the relatively low line pressures generally found
in the type cars we build.
[Edited on 8/9/11 by britishtrident]
[Edited on 8/9/11 by britishtrident]
[Edited on 8/9/11 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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hughpinder
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| posted on 9/9/11 at 08:47 AM |
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Do you know you're overbraked at the rear? Don't forget the braking force is proportional to the disk diameter, and the caliper piston
area, so if the rear calipers have smaller pistons you may have much less rear braking anyway.
My information is:
Capri front caliper piston dia=54mm, MGF rear =38, so mgf piston has 49.5% of the area, so for the same disk diameter will produce 49.5% of the
braking force. Without knowing the weight distribution and some other information its hard to know if this will be ok.
Regards
Hugh
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mad-butcher
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| posted on 9/9/11 at 08:58 AM |
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fiat uno
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Bare
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| posted on 12/9/11 at 03:35 PM |
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Erm You could always Refit the oem Spitfire drum brakes??
These Are pretty well all one would ever need :-)
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britishtrident
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| posted on 13/9/11 at 09:00 PM |
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Having said all that The best solution is more sensible bore callipers ie Rover 200 rear callipers.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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cliftyhanger
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| posted on 14/9/11 at 09:25 AM |
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quote:
Originally posted by Bare
Erm You could always Refit the oem Spitfire drum brakes??
These Are pretty well all one would ever need :-)
In fact drum brakes are remarkably effective. More than adequate when I ran my vitesse (that was a 2.5, weighed about 1000kg and the rear would still
lock up, that was with spitfire drums).
However, for a variety of reasons the spitfire handbrake is pants, plus the supply of decent brake shoes is getting very difficult.
And when it will be powered by 150+bhp, and I will be using it for all sorts of stuff with various motor clubs, a good handbrake will come in
handy
Now, off to assemble the driveshafts. Bits of mgf/metro/volvo all into a GT6 rear upright. Plus my homemade brake caliper carriers.
And I think an adjustable valve will be in order, the ones listed on here all look do-able so many thanks all....
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